Neuropsychological investigation into the carcinoid syndrome

Rationale. In patients suffering from metastatic carcinoid tumors, chronic disturbances of serotonergic metabolism are frequently present. Serotonin is supposed to influence a range of cognitive functions. Objectives. The present study evaluated the cognitive performance of carcinoid patients. Methods. In 14 patients with proven carcinoid syndrome, neuropsychological functioning was studied. Visual search, sustained attention, set shifting ability and spatial working memory were assessed using tests from the CANTAB neuropsychological battery. This was compared with the performance of matched healthy controls. Results. Plasma tryptophan levels were lower than controls. Patients showed an enhanced ability to learn new stimulus-response associations. Sustained visual attention, however, was impaired. Conclusion. Cognitive patterns were different from those found in depressive patients and partly mimicked those found in tryptophan depletion experiments. Further investigation has to point out the role of serotonergic changes in the accomplishment of affective states.